I agree with you guys ^^^^^^^
If a Ransom Rest, or something of the sort is available, eliminate the gun and ammo as being the culprit first off......if at all possible.
The problem we had, with a dozen or so senior instructors, who were match shooters, reloaders, etc., was that not a one of us had one. I thought of buying one at one point, but it was cost prohibitive for me for the number of guns I had.
So, if we had a student who was suffering from this issue, we'd pass the gun through the instructors on the range and see if it was the gun or the student. Obviously, 99.9% of the time, the student was the source. I guess once the student was totally convinced he or she was at fault, then they seemed more receptive to correcting it.
Btw contactcol, I have similar problems with the Glocks. Since most police agencies carry them nowadays, most of my work involved them. Also, since I taught and use "point & shoot" or instinctive shooting often, my problem with the Glock was my natural grip and the angle of the gun. When I hold the Glock naturally, or without concentrating on the gun or the sights, the gun's grip angle (for me) causes the gun to angle up in my hand. If I focus on the sights......no problem, and I can stitch em' right in there. Since instinctive shooting is exactly that.......a natural pull, point and shoot, the gun has to be ergonomically sound with the shooter..........most are, the Glock ?.....not for me.